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In Reply to: RE: An interesting JFET-based active XO design from TNT Audio ... posted by andyr on March 30, 2014 at 18:34:24
andyr wrote:
"2. Output DC offset can be adjusted to zero - which means there don't need to be any caps between the final XO buffer and the following power amp. (Whereas I need a cap on each amp, with the Rod Elliott XOs.)"
Most power amps have a cap at the input. Not a must to have one at the output of the crossover.
Follow Ups:
Correct, Roger - but, with this new JFET-based active XO, I can remove them from the new amp modules I am about to implement. No cap is the best cap! :-)) At least where coupling caps are concerned.
Regards,Andy
Edits: 03/31/14
Sometimes an input capacitor blocks input stage biasing (DC) from appearing at the input jack. Have you confirmed this will not be an issue with your new amps?
Dave.
andyr,
Are you bulding the new crossovers on PBCs or on prototype breadbords?
There is no PCB for these active XO circuits - so I will use my (patented!! :-)) ) construction method! :-)) This is to use a 3mm thick sheet of teflon to hold the components in place ... and do point-to-point wiring on the underneath. Teflon is easily drilled with a miniature hand-drill and withstands the heat from a soldering iron. Also, I suggest it degrades the signal much less than breadboard.
Regards,
Andy
Aha, but without a layer of copper it is difficult to have the components stay in place. Sure, I would like to see pictures when you are finished!
Here is a pic of the JFET-based phono stage that I make:
Yes, this does have a copper ground plane on the under-side ... but other components that I have used this method for - like PSes - have not ... and nothing untoward has happened.
Regards,
Andy
Andy,
What are these large film caps? Are they part of the frequency setting or supply bypass?
That is an early picture - v2 of the 'Muse'. The circuit is currently at v4, so I am using different caps now.
Regards,
Andy
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